The mourning cloak butterfly, in for the winter.
I got down to the river about 2:30 p.m. I was too late; the angle of the sun didn't light up the ground anywhere. My little dragonflies were nowhere in evidence. In fact, without the sun on the ground I saw one fly and a tiny spider and a baby centipede under a rock. That was it.
All this raises the question, “Where do the bugs go in winter?” They are ectothermic (cold blooded) and in danger of freezing in even a light frost. Ice forming ruptures cell walls and is usually deadly.
To be blunt, most adult insects, having lived out their lives and reproduced have fulfilled their destiny and just die.
Others, like the famous Monarch butterfly, migrate to overwinter in warmer climes. The really interesting thing about them is, unlike birds, their navigation is all instinctive. The ones that migrate to Mexico were not born there so the navigation is all inherited.
The variegated meadowhawk dragonfly dries out for survival.
Some insects nearly mummify themselves, getting rid of as much water from their cells as possible. Less water means less crystallization. I suspect that is how my variegated meadowhawk dragonflies manage surviving frosty nights. Looking through my photo gallery I find most late winter specimens abdomens are translucent and nearly empty.
Some insects actually produce an antifreeze in their blood as the temperatures drop. I've read that is how fungus gnats manage in the cold.
A different strategy is to put their eggs somewhere they will not freeze, like running water. It's the strategy of mayflies (order Ephemeroptera
), which live for only a couple of days as adults merely to mate and lay eggs before they fall exhausted onto the water to drown and feed the fish.
The caddis fly larva carrying around its little shelter made of grains of sand underwater.
Caddisflies (order Trichoptera
) lay eggs in water as well, their larvae building tiny structures from stream debris they carry around. Still others live out the cold months in the soil or underneath rocks, below the level where frost reaches.
Regardless of their strategy, the chemical process of life are slowed down in the cold and bugs are much less active. Many will sit out the winter as eggs or pupae (cocoons). Others like adult mourning cloak butterflies can stay dormant for months but warm up on sunny winter days and briefly brighten our days with an appearance.